The present invention relates to cutting apparatus and, in particular, to apparatus for cutting grooves in the top of stair steps to provide a slip-resistant top surface on the stair step.
Various grooving machines for cutting grooves in the tops of stair steps are known. For example, in U.S. Pat. No. 1,845,666, issued Feb. 16, 1932, to Jennings, a stair tread grooving machine is shown including a housing in which a plurality of grooving blades are coupled to an axle which is positioned between two bearing members fixed to the housing. The apparatus provides wheels so that the entire stair tread grooving machine can be rolled along the top of a stair step as the cutting process proceeds. A motor is placed on top of the housing and provides rotational motion to the grooving blades via a pulley and belt apparatus. The positioning means are vertically and horizontally adjustable. However, the method by which this adjustment takes place requires complex support, bearing and housing apparatus. Furthermore, this apparatus does not require any blade cooling apparatus and, consequently, no cooling means is incorporated. Without liquid cooling means, such as that in the present invention, substantial quantities of dust are produced which constitute a potential health hazard to the operator. To partially overcome this deficiency, the apparatus includes a vacuum system to collect the dust. Such apparatus is not required in the present invention. Finally, no means is provided for maintaining the face guide against the front face of the step to insure that the grooves will be cut parallel to the face of the step.
A similar grooving machine apparatus was disclosed in U.S. Pat. No. 2,709,878, issued June 7, 1955, to Olson. The principal difference in Olson when compared to Jennings discussed above is in the means by which the cutting blades are adjusted upwardly or downwardly to cut deeper or shallower grooves in the top of the stair step. Thus, in Olson, an upper telescoping housing supports the motor while a lower telescoping housing supports the blades as associated bearings and support apparatus. The lower and upper telescoping housings are movable relative to one another to lower or raise the blades. Clearly, Olson involves even more complexity without really solving any of the problems in the Jennings patent.
In yet another patent, U.S. Pat. No. 3,464,737, issued Sept. 2, 1969, to Haase, et al, a road grooving machine is shown having diamond cutting blades which utilize liquid coolant, such as water, which is sprayed from a plurality of nozzles onto the blades to cool them during the grooving process.
In each of the above patents, the drive means includes not only the motor but also requires a substantial amount of linkage, including pulleys and belts, between the axle of the drive motor and the grinding axle. None of the above inventions provide direct drive. Furthermore, as previously mentioned, each of the above grooving apparatus incorporates wheels by which the grooving apparatus is rolled along the surface to be grooved. However, the inclusion of wheels substantially increases the complexity of the apparatus required to raise or lower the cutting blades so that a particular depth of groove can be selected.
The reason that these patents generally incorporated wheels is believed to be because it was felt that a substantial amount of weight was required to press the cutting blades against the surface to be grooved. Without the incorporation of wheels, the increased friction caused by the required downward force would cause the above devices to be very difficult to move along the step as the grooving took place. The grit resulting from the grooving added to this problem and caused even more friction and made use of wheels even more necessary. The utilization of a simple, lightweight, portable grooving apparatus without wheels and the associated complex apparatus, where the downward force applied to force the grooving blades into the step surface is provided by the operator, was apparently not contemplated in any of the above inventions. Rather, the downward force was largely a result of the weight of the motor and other apparatus placed directly above the blades. Of course, such arrangement required linkages between the motors and the blades. Furthermore, none of the above inventions provided for any component of force to be applied by the operator to press the face guide against the front face of a stair step to insure that the grooves were, in fact, parallel to the front face of the stairs. Indeed, with the stair step grooving apparatus patents discussed above, it is possible for the grooves to be cut at a slant relative to the front face of the stair if initial alignment is incorrect. In such a case, the direction of the grooves being cut is determined not by the face guide but rather by the blades as directed and positioned in the just cut grooves. This result would occur because the blades tend to follow the grooves cut in a longitudinal fashion so that the initial direction of cut would be maintained. The use of wheels further enforces this tendency to maintain misalignment.
By contrast, the present invention overcomes these problems and deficiencies by providing a novel stair grooving apparatus which includes a radially attached handle whereby an operator can press directly downward on the apparatus to press the rear skid against the top surface to be grooved and a second, laterally extending handle which is positioned in such a way that, as the operator presses downward on the second handle, a vertical as well as a horizontal force is simultaneously applied to cause the front skid of the present invention to press against the top surface at the same time that the face guide member is pressed against the face of the stair step being grooved. In addition, much of the complexity of the prior step grooving apparatus is eliminated since the present invention does not utilize wheels, but rather utilizes skids.
Skids have a significant advantage over wheels in that skids do not tend to maintain a particular direction. Thus, if an incorrect direction in the grooving occurs, correction of that misdirection is more easily achieved in that the skids do not tend to inhibit the change of direction as wheels generally do. Furthermore, the utilization of skids rather than wheels permits less lateral force to be applied to position the face guide against the face of the stair step. Finally, and most obviously, the utilization of skids rather than wheels allows a greatly simplified height adjustment mechanism to be incorporated which not only reduces the complexity of the raising and lowering mechanism, but also greatly decreases the weight of the groove cutting apparatus.
In addition to the above advantages, the present invention incorporates a liquid cooling system whereby a plurality of orifices are provided in the housing with a plurality of nozzles provided, one for each orifice. The plurality of nozzles are then coupled via coupling apparatus to a source of cooling fluid which is sprayed by the nozzles against the cutting or grooving blades to cool the blades.
While the use of the fluid is primarily for the purpose of cooling, the utilization of a fluid has a significant secondary purpose, namely, to provide a lubricant to decrease the friction between the skids and the surface of the stair step to be cut. The fine grit obtained as the concrete or other material from which the step is made is cut provides additional lubrication effect when it is wetted by the fluid. Thus, the fine grit plus the presence of the fluid allows the skids to slide much more freely across the top surface of the stair step than would be possible without the fluid.
Finally, the utilization of liquid cooling also has another secondary effect, namely, suppressing dust and other pollutants which can be hazardous to the health of the operator. Even though the Haase, et al patent described above incorporates a liquid cooling system which has the secondary effect of suppressing dust, because the Haase, et al patent utilizes wheels, the liquid does not act as a lubricant to assist in moving the apparatus along the surface to be grooved. By contrast, the present invention utilizes the liquid and the resulting dust and small particles from the grinding to provide lubrication between the step and the skids to thereby assist in moving the apparatus more easily along the stair step.
It will be appreciated that, without the liquid and fine grit as a lubricant on top of the stair step, the incorporation of skids instead of wheels on either of the two patents discussed above would have been impractical since it would be very difficult to move the machine along the top of the stair as the necessary downward force was applied.